EFFECT OF VERAPAMIL ON ENDOTHELIN-1-INDUCED PROLIFERATION IN CULTUREDRAT MESANGIAL CELLS

The effect of verapamil, a calcium channel blocker, on endothelin-1 (E T-1)-induced mesangial cell proliferation was assayed. Rat mesangial c ells (primary cultures) were maintained in 0.5% fetal calf serum mediu m for 2 days and then incubated with ET-1 and verapamil for 24 h. ET-1 induced a dose-dependent [H-3]thymidine uptake (peak at 10(-7) M; 773 +/- 85% over basal, serum-deprived cells), protein synthesis (ET-1 10 (-7) M; 267 +/- 23% over basal) and cell number (ET-1 10(-7) M; 214 +/ - 23% over basal). Verapamil inhibited the ET-1-induced increase in bo th thymidine uptake and protein synthesis in a dose-dependent manner. Verapamil 10(-5) M reduced by 82% ET-1 10(-8) M-stimulated thymidine u ptake, and totally abolished the increase in protein synthesis and cel l number (100% inhibition). ET-1 10(-8) M induced expression of c-fos proto-oncogen mRNA 30 min after starting stimulation. Verapamil 10(-5) M did not completely inhibit ET-1-induced c-fos mRNA expression. ET-1 10(-8) M induced expression of proliferating cell nuclear antigen (PC NA) in cells after 24 h of incubation. Verapamil also inhibited endoth elin-induced PCNA immunoreactivity. These data show a dissociation bet ween the effects of verapamil on ET-1-induced cell proliferation, DNA synthesis, c-fos mRNA expression and PCNA expression.